Artificial Lift Strategy Selection Within Field Development Planning

Abstract

At the stage of field development planning the choice of the lift method largely affects the overall evaluation of the project efficiency. This effect is derived not only from different OPEX required for artificial lift as determined by the energy characteristics and equipment service life but also from optimal utilization of surface facilities. The paper describes the approach to selecting the lift method on the basis of simultaneous problem solving used to estimate the optimal production flow rates and OPEX for every method under study subject to complicating factors and CAPEX for surface infrastructure. The described approach is based on the analytical models for assessment of feasible flow rates and power consumption for various lifting mechanisms given the possible geology and process constraints during the full field life cycle. The main differences from the conventional approach to selecting the lift method consist in the following: no need for specialized software tools for selecting downhole pumping equipment; flexibility in case of significant changes in the well production conditions which are very typical of greenfields with hard-to-recover reserves; option for simultaneous solution to the problem of selecting the field depletion strategy and optimal production method by means of calculating the realistic bottom-hole pressures at the stage of flow simulations. The paper presents a case study from introduction of this approach to selecting the lift method for the wells of R. Trebs' oil field. The field is rather deep with productivity proven in carbonate reservoirs with mixed type of porosity (fractured-vuggy-porous) and low matrix permeability. The fracture intensity and vugginess are characterized by lateral heterogeneity. The application of the conventional approach to selecting the lift method with the help of ‘average' wells is problematic due to a wide scatter in future well productivity numbers. In this case the optimal producing method was selected not only for the individual wells but also for the full field during its life cycle. The selection of the production method was also based on the probable predicted problems typical for this field (paraffins, salts and corrosion) and cost evaluation for preventive measures. The modeled scenarios defined the best arrangements for acquisition and lease of equipment depending on the cost of the pumping units, construction of repair shops and logistics. The sensitivity analysis was run to account for the uncertainties in the source input data. The results of this analysis were presented as applicability maps for each of the methods on the basis of the key production parameters. The proposed approach was implemented in a computational module which may be utilized to select the optimal production method for wells in fields with complex geology and considerable variability in well behavior. The evaluation of the realistic or feasible project targets may be used to adjust the target production profiles in flow dynamic simulators.